The POST /api/v2/recordings/screen endpoint is returning a 400 Bad Request with the message “Invalid recording payload structure” when the concurrent thread count exceeds 20 in our JMeter load test. This happens immediately after the WebSocket connection establishes successfully, but before the actual screen data begins streaming. The error occurs consistently in the ap-southeast-1 region, regardless of whether we use the latest Genesys Cloud Web SDK or a custom Node.js client.
Our test setup simulates a high-concurrency scenario where multiple virtual agents initiate screen sharing sessions simultaneously to stress-test the media ingestion pipeline. We are using JMeter 5.6 with the WebSocket Sampler plugin, configured to send the initial handshake and metadata payload within the first 500ms of connection. The payload includes the required recordingId and sessionId, but the 400 error suggests the server-side validation is rejecting the request format or timing. We have verified the JSON structure against the API documentation, and it matches the schema exactly for single-thread tests.
We are trying to determine if there is a hidden rate limit or a specific timeout window for the screen recording initiation phase that is not documented in the public API specs. The logs show the connection is accepted, but the metadata upload fails under load. Is there a known issue with the screen recording API handling concurrent initiation requests, or are we missing a specific header or timing constraint in our JMeter script? We need to understand the exact threshold where the API starts rejecting valid payloads to adjust our capacity planning for the upcoming quarter.
I typically get around this by checking the payload chunking logic in the test script. The 400 error often stems from malformed JSON headers during high concurrency.
- Validate that the
Content-Type is strictly application/json.
- Ensure the recording metadata matches the schema in the API docs.
- Add a small delay between WebSocket handshake and the first data packet.
The quickest way to solve this is to enforce strict payload serialization in the JMeter setup before the WebSocket handshake completes. The 400 error often appears because concurrent threads generate malformed JSON headers when the serialization process races against the connection establishment.
In my recent load tests, I found that adding a explicit JSON stringify step for the metadata object prevents schema mismatches. The Genesys Cloud API expects a very specific structure for screen recordings, and any deviation causes an immediate rejection. Here is the JSR223 PreProcessor code I use to validate the payload structure before sending:
import groovy.json.JsonOutput;
// Extract metadata from JMeter variables
String meta = vars.get("recordingMetadata");
// Ensure strict JSON format
String formattedMeta = JsonOutput.prettyPrint(meta);
// Set the body for the subsequent request
sampler.setBodyAsString(formattedMeta);
// Log for debugging
log.info("Validated Payload: " + formattedMeta);
This ensures the Content-Type is correctly interpreted and the body matches the API schema. Also, check the API rate limits for the ap-southeast-1 region. High concurrency can trigger throttling before the actual data stream starts. A small delay of 50-100ms between the WebSocket open event and the first metadata POST usually helps stabilize the connection. This aligns with the suggestion above about validating headers, but adds the serialization safety net needed for high-throughput tests. Make sure your JMeter thread group is not exceeding the WebSocket connection limits per IP address, as that can also manifest as a 400 error during the initial setup phase.
This seems like a standard race condition in the JMeter thread group configuration rather than a Genesys API limitation. The 400 Bad Request during the initial handshake usually indicates that the client is attempting to send the screen recording metadata payload before the WebSocket connection state has fully transitioned to “OPEN” on the server side. In high-concurrency scenarios like JMeter, threads often overlap their initialization steps.
The solution is to enforce a strict synchronization point in the JMeter script. You need to ensure the WebSocket listener explicitly waits for the “Connection Established” event before triggering the POST request for the recording metadata.
Here is the recommended JMeter BeanShell/JSR223 PreProcessor logic to validate the connection state:
// JSR223 PreProcessor in JMeter
import org.apache.jmeter.protocol.websocket.sampler.WebSocketSampler
// Verify WebSocket connection status before proceeding
def wsSampler = ctx.getCurrentSampler()
if (wsSampler.getConnectionState() != "OPEN") {
throw new Exception("WebSocket not ready. Aborting payload send.")
}
// Ensure payload structure matches Genesys Cloud schema exactly
def payload = new groovy.json.JsonBuilder(
recordingType: "screen",
startTime: new Date().getTime(),
// Include all mandatory fields from the API spec
)
vars.put("finalPayload", payload.toString())
Additionally, check your genesyscloud Terraform configuration if you are managing any related recording policies. Ensure the max_recording_duration and allowed_formats in your genesyscloud_recording_policy resource align with what JMeter is simulating. Mismatched format expectations can also trigger 400 errors, though less commonly than connection state issues.
The ap-southeast-1 region latency might be exacerbating the race condition. Adding a Constant Timer of 100-200ms after the WebSocket connect sampler but before the metadata POST often resolves this in load tests. This mimics real-world client behavior where the UI initializes before streaming data.